A DIN rail is a standardized 35 mm wide metal rail with a top-hat shaped cross section. It is widely used, especially in Europe, for mounting circuit breakers and industrial control equipment inside equipment racks. In addition to the popular 35 mm top-hat rail several less widely used types of top-hat mounting rails have also been standardized. Top-hat rails are usually mounted in a horizontal orientation to a flat vertically oriented surface. In such an orientation the top-hat cross section provides an upwardly oriented edge and a downwardly oriented edge. The forgoing structure provides a strong stable mounting rail on which to mount enclosures that house a myriad of devices.
Attachment of enclosures to the rail is typically accomplished by sizing a horizontal channel in a surface of an enclosure that is slightly greater in width than the width of the rail. Typically a downwardly extending lip on an upper sidewall of the channel engages with the upwardly oriented edge of the rail. Thus, weight of the enclosure, and device housed therein, pull the downwardly extending lip into contact with the upwardly oriented edge of the rail and thereby hold the enclosure to a vertical surface to which the rail is attached.
Such a system, however, has the potential for the enclosure to become unintentionally disengaged from the rail if the enclosure is inadvertently bumped in a specific manner. For example, if the bump causes the downwardly extending lip on the channel to be momentarily lifted above the upwardly oriented rail edge the lip may not reengage with the edge upon resettling. If this happens the enclosure will no longer be retained on the rail and will fall with possibly damaging consequences.
To improve retention to the rail some rail mounting systems use a movable lip on one side of the channel and a stationary lip on the other side of the channel. Such a system may successfully prevent the inadvertent disengagement discussed above. Having a lip fixedly attached to either side of the channel, however, requires that the enclosure be tilted relative to the rail when installing the enclosure onto the rail. This tilting action allows the fixed lip to be positioned behind the edge of the rail before tilting the enclosure back to a square orientation with the rail, wherein the lip engages with the rail as described above. Some applications however have limited space available above and below the mounting location of the enclosure precluding the tilting necessary to engage the lip beyond the edge of the rail.
Accordingly there is a need in the art for an enclosure to rail mounting system that doesn't require clearance above or below a mounting location of the enclosure.